Topcoating composition and film-forming process by use of the same

ABSTRACT

The present invention provides a topcoating composition prepared by incorporating a specified organosilicate and/or its condensate into a specified organic coating composition, a film formed from said topcoating composition being such that a surface of the film, which has been subjected to an acid treatment, shows a contact angle to water of 70° or less; and a film-forming process which comprises coating said topcoating composition onto a substrate to form a film, followed by treating the surface of the film with an acid. The present invention provides such effects that the film obtained according to the present invention shows good weather resistance and good stain resistance.

The application is a Continuation of prior U.S. application Ser. No.08/235,347, Apr. 29, 1994, now abandoned, which is acontinuation-in-part of application PCT/JP93/01360, Sep. 22, 1993.

FIELD OF THE INVENTION

The present invention relates a topcoating composition and afilm-forming process by use of the topcoating composition, which arecapable of forming a coated film having good weather resistance and goodstain resistance.

BACKGROUND OF THE INVENTION

An outdoor coating composition having good weather resistance hasconventionally been applied onto outdoor substrates such as buildingstructures, displays, guard fences, instruments, machines and the likefor the purpose of decoration or protection.

The outdoor coating composition used at present may include, forexample, polyurethane resin based coating composition, fluorocarbonresin based coating composition and the like, but use of these coatingcompositions results in such disadvantages that a surface of a coatedproduct may easily be stained and show poor appearance by influence dueto dust, iron powder, rain, particularly acid rain, sunlight, etc.during outdoor exposure.

Besides the above coating compositions, a silicone resin based coatingcomposition containing an alkoxysilane group-containing polymer as aresin component has been used as a highly weather-resistant coatingcomposition. When a period of outdoor exposure is as long as six monthesor so, stain on the surface of a film formed from the above coatingcomposition may be reduced, but the use of the above coating compositionshows such a problem that the surface of the film formed therefrom mayeasily be stained when the period of outdoor exposure is shorter thansix monthes.

As an example of a method of preventing stain on the film surface,Japanese Patent Application Laid-Open No. 221282/86 discloses a processwhich comprises coating an alkylsilicate solution in an organic solventonto the surface of a molded product and a process which comprisesincorporating alkylsilicate into a molded product of a thermoplasticresin. However, the above methods had such drawbacks that the filmprovided by the above methods shows poor properties in retension ofstain resistance and durability.

The present inventors made intensive studies for the purpose of solvingthe above problems to find out that a coating composition obtained byincorporating an organosilicate and a condensate thereof into an organiccoating composition provides a film hardly stained or showing good stainresistance, resulting in accomplishing the present invention.

DISCLOSURE OF THE INVENTION

That is, the present invention relates to a topcoating compositionprepared by incorporating an organosilicate represented by the generalformula: ##STR1## where R is same or different and is hydrogen atom or amonovalent hydrocarbon group having 1 to 10 carbon atoms, and/or itscondensate into an organic coating composition, a film formed from saidtopcoating composition being such that a surface of the film, which hasbeen subjected to an acid treatment, shows a contact angle to water of70° or less; and a film-forming process which comprises coating saidtopcoating composition onto a substrate to form a film, followed bytreating the surface of the film with an acid.

PREFERRED EMBODIMENTS FOR THE PRACTICE OF THE INVENTION

The organic coating composition used in the topcoating composition ofthe present invention may include a solvent-based organic coatingcomposition, water-based organic coating composition, liquid organiccoating composition free of solvent and water, powder coatingcomposition, etc.

The solvent based organic coating composition may include a reactivelycurable coating composition containing a reactively curable organicresin as a resin component.

The reactively curable coating composition may include one prepared bydissolving or dispersing a curable resin composition, which is capableof being reactively cured by itself to form a crosslinked filmstructure, into an organic solvent.

The reactively curable coating composition used in the present inventionmay be such that the surface of a finally formed cured film, which hasbeen subjected to a treatment with an aqueous sulfuric acid, has acontact angle to water of 70° or less.

The reactively curable coating composition is not particularly limitedso long as the above conditions are satisfied, and may arbitrarily beselected from conventionally used ones. Of these, a coating compositioncontaining a hydroxyl group-containing resin as a base resin ispreferred, because the coating composition is capable of forming a filmshowing good stain resistance during a long period of outdoor exposuretime.

The hydroxyl group-containing resin may specifically include resins suchas fluorocarbon resin, acrylic resin, polyester resin, alkyd resin,silicone resin and the like, and modified resins such as polyestermodified acrylic resin and the like. Of these, fluorocarbon resin andacrylic resin are preferred, because the film obtained by use of theseresins shows good stain resistance.

The hydroxyl group-containing fluorocarbon resin may include onesobtained by copolymerizing a hydroxyl group-containing radicallypolymerizable unsaturated monomer(a), a fluoroolefin(b) and, if needed,other radically polymerizable unsaturated monomer(c).

The hydroxyl group-containing radically polymerizable unsaturatedmonomer(a) may include ones having a radically polymerizable unsaturateddouble bond radically copolymerizable with fluoroolefin and hydroxylgroup, and specifically may include, for example, hydroxyalkyl vinylether such as hydroxylethyl vinyl ether, hydroxypropyl vinyl ether,hydroxybutyl vinyl ether, hydroxypentyl vinyl ether and the like; andhydroxyallyl ether such as ethylene glycol monoallyl ether, diethyleneglycol monoallyl ether, triethylene glycol monallyl ether and the like.

The fluoroolefin(b) used as above may include ones represented by thegeneral formula: ##STR2## where R₁, R₂ and R₃ are H, F and Clrespectively, and may be same or different, and may specificallyinclude, for example, vinyl fluoride, vinylidene fluoride,chloroethylene trifluorides, ethylene tetrafluorides and the like. Ofthese, ethylene tetrafluorides and chloroethylene trifluorides arepreferred in that a film having good durability and good stainresistance is obtained.

The other radically polymerizable unsaturated monomer(c) may includeones having an unsaturated double bond radically copolymerizable withthe above fluoroolefin, and may be selected from conventionally knownmonomers depending on film performances as required. Specific examplesthereof may include α-olefins such as ethylene, propylene, isobutylene,butylene-1 and the like; vinyl ethers such as ethyl vinyl ether,isobutyl vinyl ether, butyl vinyl ether, cyclohexyl vinyl ether and thelike; aliphatic vinyl esters such as vinyl acetate, vinyl lactate, vinylburylate, vinyl isobutylate, vinyl caproate, vinyl pivarate, vinylcaprate and the like; fatty acid isopropenyl esters such as isopropenylacetate, isopropenyl propionate and the like; and the like.

The hydroxyl group-containing fluorocarbon resin may have carboxylgroup. The above carboxyl group may be introduced, for example, byaddition reaction of a part of hydroxyl groups in the hydroxylgroup-containing fluorocarbon resin with a polybasic acid anhydride suchas itaconic anhydride, succinic anhydride or the like.

In addition to the above, the hydroxyl group-containing fluorocarbonresin may include polymers obtained by copolymerizing a monomer(d)having perfluoroalkyl group or perfluoroalkenyl group at one end andethylenical double bond at other end, a hydroxyl group-containingradically polymerizable unsaturated monomer(e), and other radicallypolymerizable unsaturated monomer(f).

Preferable examples of the monomer(d) having perfluoroalkyl group orperfluoroalkenyl group at one end and ethylenical double bond at otherend may include perfluorobutylethyl methacrylate, perfluorooethylethylmethacrylate, perfluoroisononylethyl methacrylate, perfluorodecylethylmethacrylate and the like.

Preferable examples of the hydroxyl group-containing radicallypolymerizable unsaturated monomer(e) may include 2-hydroxyethylacrylate, hydroxypropyl acrylate, 2-hydroxyethyl methacrylate,hydroxypropyl methacrylate and the like.

Preferable examples of the other radically polymerizable unsaturatedmonomer(f) may include C₁₋₁₈ alkyl esters of acrylic acid or methacrylicacid such as methyl acrylate, ethyl acrylate, propyl acrylate, isopropylacrylate, butyl acrylate, hexyl acrylate, octyl acrylate, laurylacrylate, cyclohexyl acrylate, methyl methacrylate, ethyl methacrylate,propyl methacrylate, isopropyl methacrylate, butyl methacrylate, hexylmethacrylate, octyl methacrylate, lauryl methacrylate and the like;ethylenically unsaturated carboxylic acids such as acrylic acid,methacrylic acid and the like; vinyl aromatic monomers such as styrene,α-methylstyrene, vinyl toluene and the like; amide compounds of acrylicacid or methacrylic acid and derivatives thereof; acrylonitrile,methacrylonitrile and the like. The hydroxy group-containing acrylicresin may include ones obtained by copolymerizing the above hydroxylgroup-containing radically polymerizable unsaturated monomers(a) and/or(e), and C₁₋₁₈ alkyl ester of acrylic acid or methacrylic acid, or otherradically polymerizable unsaturated monomer(g).

Examples of the other radically polymerizable unsaturated monomer(g) mayinclude ethylenically unsaturated carboxylic acids such as acrylic acid,methacrylic acid and the like; vinyl aromatic monomers such as styrene,α-methylstyrene, vinyl toluene and the like; amide compounds of acrylicacid or methacrylic acid and derivatives thereof; acrylonitrile,methacrylonitrile and the like. The above hydroxy group-containing resinmay have a number average molecular weight of about 2,000 to 100,000,preferably about 5,000 to 80,000. When the above molecular weight isless than about 2,000, both durability and retension of stain resistanceare undesirably reduced. On the other hand, then more than 100,000,compatibility with the curing agent and alkyl silicate becomes poor andstorage stability of the coating composition is undesirably reduced.

The hydroxyl group-containing resin may have a hydroxyl number of about20 to 200, preferably about 50 to 150. When the hydroxyl number is lessthan about 20, the film shows undesirably poor water resistance andretension of stain resistance. On the other hand, when more than 200,the film shows undesirably poor durability, water resistance and stainresistance.

The hydroxyl group-containing resin may be used in combination with areactive curing agent such as amino resin, polyisocyanate compound,blocked polyisocyanate compound and the like.

The amino resin may include a methyloled amino resin obtained byreaction of aldehyde with an amino component such as melamine, urea,benzoguanamine, acetoguanamine, steroguanamine, spiroguanamine,dicyandiamide and the like. Examples of aldehyde may includeformaldehyde, paraformaldehyde, acetoaldehyde, benzaldehyde and thelike. The methyloled amino resin may be etherified with a suitablealcohol to be used. Examples of the alcohol used in ethersification mayinclude methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propylalcohol, n-butyl alcohol, i-butyl alcohol, 2-ethyl butanol, 2-ethylhexanol and the like.

The polyisocyanate compound is a compound having two isocyanate groupsin one molecule, and may include, for example, aliphatic compounds suchas hexamethylene diisocyanate, trimethylhexamethylene diisocyanate andthe like; alicyclic compounds such as hydrogenated xylylenediisocyanate, isophorone diisocyanate, cyclohexane diisocyanate and thelike; aromatic compounds such as tolyrene diisocyanate, diphenylmethanediisocyanate and the like; and the like.

The blocked polyisocyanate compound may include ones obtained byblocking the above polyisocyanate compound with a lactam blocking agentsuch as ε-caprolactam, an alcohol blocking agent such as ethanol,propanol, butanol and the like, or an oxime blocking agent such asacetoxime.

A mixing ratio between the hydroxyl group-containing resin and the aminoresin is such that the hydroxyl group-containing resin is in the rangeof 90 to 40% by weight, preferably 80 to 50% by weight, and the aminoresin is in the range of 10 to 60% by weight, preferably 20 to 50% byweight based on a total weight of both thereof. When the mixing ratio isoutside the above ranges, the film is undesirably reduced in stainresistance, water resistance, weather resistance, etc.

A mixing ratio between the hydroxyl group-containing resin and the(blocked) polyisocyanate compound is such that an isocyanate group inthe (blocked) polyisocyanate compound is in the range of about 0.6 to1.5 equivalents, preferably about 0.8 to 1.2 equivalents based onhydroxyl group in the hydroxyl group-containing resin. When theisocyanate group is less than about 0.6 equivalent, the film isundesirably reduced in weather resistance, stain resistance and waterresistance. On the other hand, when the isocyanate group is more thanabout 1.5 equivalents, the film is undesirably reduced in stainresistance, weather resistance, etc.

In addition to the above-mentioned ones, the curable resin compositionin the reactively curable coating composition used in the presentinvention may include ones obtained by incorporating a curing catalystinto a resin or resin mixture (hereinafter may be referred to as "a baseresin") containing silanol group and/or hydrolyzable silyl group,hydroxyl group and epoxy group as the essential functional groupcomponent. The curable resin composition is capable of forming such afilm that the base resin is combined with organosilicate or a condensatethereof, and provides such advantages as to show good stain resistanceover a long period of time. The curable resin composition is explainedin the following.

The hydrolyzable silyl group contained in the base resin used in theabove coating composition is a residual group to form a hydroxysilanegroup by hydrolysis in the presence of water, and may include, forexample, C₁₋₅ alkoxy group; aryloxy group such as phenoxy group,tolyloxy group, paramethoxyphenoxy group, paranitrophenoxy group,benzyloxy group and the like; acyloxy group such as acetoxy group,propyonyloxy group, butanoyloxy group, benzoyloxy group, phenylacetoxygroup, formyloxy group and the like; residual groups represented by--N(R₄)₂, --ON(R₄)₂, --ON═C(R₄)₂ and --NR₅ COR₄, wherein R₄ is same ordifferent respectively and represents C₁₋₈ alkyl group, aryl group suchas phenyl group and aralkyl group such as benzyl group, and R₅represents C₁₋₈ alkyl group such as methyl, ethyl, propyl, butyl,pentyl, heptyl and the like; and the like.

The base resin may include, for example, 1 a resin mixture (hereinaftermay be referred to as "a resin 1") containing a hydroxylgroup-containing resin (A), an epoxy group-containing resin (B) and aresin (C) containing silanol group and/or hydrolyzable silyl group; 2 aresin mixture (hereinafter may be referred to as "a resin 2") containingthe epoxy group-containing resin (B) and the resin (C) containingsilanol group and/or hydrolyzable silyl group, wherein either one orboth of the resin (B) and the resin (C) may have hydroxyl group; 3 aresin (hereinafter may be referred to as "a resin 3") containinghydroxyl group, epoxy group, silanol group and/or hydrolyzable silylgroup; and the like.

The resin 1:

The hydroxyl group-containing resin (A) may have two or more hydroxylgroups on an average in one molecule, and preferably may have a numberaverage molecular weight of 1,000 to 100,000, preferably 3,000 to80,000. When the number of hydroxyl group is less than two on anaverage, curing properties or gel fraction becomes undesirably poor. Thenumber of hydroxyl group is preferably 400 or less on an average fromthe standpoints of stain resistance, water resistance, etc. When thenumber average molecular weight is less than 1,000, the film shows poorweather resistance, stain resistnace, etc. On the other hand, when morethan 100,000, compatibility with other components is reduced, resultingin non-uniform curing and poor stain resistance.

The hydroxyl group-containing resin (A) may include conventionally usedresins, and preferably may include vinyl polymer from the standpoints ofweather resistance and stain resistance.

The vinyl polymer may include a (co)polymer obtained by radicallypolymerizing, for example, a hydroxyl group-containing polymerizableunsaturated monomer (h) and, if needed, other polymerizable unsaturatedmonomer (i).

The hydroxyl group-containing polymerizable unsaturated monomer (h) mayinclude, for example, the following (h-1) to (h-5).

The (h-1) may include hydroxyalkyl vinyl ether such as hydroxybutylvinyl ether.

The (h-2) may include allyl alcohol and methallyl alcohol.

The (h-3) may include hydroxyalkyl ester of (meth)acrylic acid, forexample, hydroxyethyl (meth)acrylate, hydroxypropyl meth(acrylate),hydroxybutyl (meth)acrylate, etc.

The (h-4) may include (poly)alkylene glycol monoacrylate such asethylene glycol monoacrylate, polyethylene glycol monoacrylate and thelike.

The (h-5) may include addition products of the (h-1) to (h-4) withlactones such as ε-caprolactone, γ-valerolactone and the like.

The other polymerizable unsaturated monomer (i) may include, forexample, C₁₋₂₄ alkyl or cycloalkyl esters of (meth)acrylic acid such asmethyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, hexyl(meth)acrylate, octyl (meth) acrylate, lauryl (meth)acrylate, cyclohexyl(meth) acrylate and the like; vinyl aromatic compounds such as styrene,vinyltoluene and the like; perfluoroalkyl (meth)acrylates such asperfluorbutylethyl (meth) acrylate, perfluoroisononylethyl(meth)acrylate, perfluorooctylethyl (meth)acrylate and the like;(meth)acrylonitriles, olefins, fluoroolefins, vinyl esters, cyclohexylor alkyl vinyl ether olefins, vinyl esters, cyclohexyl or alkyl vinylethers, allyl ethers, and the like.

The epoxy group-containing resin (B) may have 2 to 300 epoxy groups onan average in one molecule, and preferably may have a number averagemolecular weight of 120 to 100,000, preferably 240 to 60,000. When thenumber of epoxy group is less than two on an average, weather resistanceand stain resistance become indesirably poor. It is difficult to obtaina compound having a number average molecular weight less than 120. Onthe other hand, when the number average molecular weight is more than100,000, compatibility with other components becomes poor, resulting inthat the resulting film is undesirably reduced in weather resistance,stain resistance, etc.

The expoxy group-containing resin (B) may preferably includehomopolymers of an epoxy group-containing polymerizable unsaturatedmonomer (j) such as alicyclic vinyl monomers represented by the generalformulas (4) to (18) as disclosed in Japanese Patent ApplicationLaid-Open No.160879/90, and copolymers of the monomer (j) with otherpolymerizable unsaturated monomer (i).

The resin (C) containing silanol group and/or hydrolyzable silyl groupmay preferably include homopolymers or copolymers with otherpolymerizable unsaturated monomer (i) of a silane monomer (k-1) havingsilanol group and/or hydrolyzable silyl group such asγ-(meth)acryloxypropyl trimethoxysilane, γ-(meth)acryloxypropyltriethyoxysilane, γ-(meth)acryloxypropyl trisilanol,γ-(meth)acryloxypropylmethyl dimethoxysilane, vinyltrimethoxysilane,vinyl triethoxysilane, 2-styrylethyl trimethoxysilane,allyltriethoxysilane, and the like; homopolymers or copolymers of asiloxane macromonomer (k-2), for example, a polysiloxane macromonomerdisclosed in Japanese Patent Application Laid-Open No. 160879/90, havingsilanol group and/or hydrolyzable silyl group and a polymerizableunsaturated group and obtained by reacting the silane compound (k-1)with trialkoxy or trihydroxysilane compound such asmethyltrimethoxysilane, phenyltrimethoxysilane and methyltrisilanol;diphenylsilane diol, and the like.

A mixing ratio of the resins (A), (B) and (C) is preferably such thatthe resin (A) is in the range of 5 to 95% by weight, preferably 20 to80% by weight, the resin (B) is in the range of 95 to 5% by weight,preferably 80 to 20% by weight, and the resin (C) is in the range of 0.1to 80% by weight, preferably 1 to 20% by weight based on a total weightof the resins (A), (B) and (C) from the standpoints of weatherresistance, stain resistance, etc. respectively.

Resin 2:

The epoxy group-containing resin (B) and the resin (C) containingsilanol group and/or hydrolyzable silyl group are the same as in theresin 1.

In the resin 2, either one or both of the resin (B) and the resin (C)may have hydroxyl group, and introduction of hydroxyl group into theresin (B) and the resin (C) may be carried out by using the hydroxylgroup-containing polymerizable unsaturated monomer (h) as an essentialmonomer component. In this case, a number of hydroxyl group containedtherein may preferably be one or more on an average, preferably 400 orless on an average. A number average molecular weight of the resin, intowhich hydroxyl group has been introduced, may desirably be 1,000 to100,000, preferably 3,000 to 60,000 respectively.

A mixing ratio of the resins (B) and (C) may be such that the resin (B)is in the range of 5 to 95% by weight, preferably 20 to 80% by weight,and the resin (C) is in t he range of 95 to 5% by weight, preferably 80to 20% by weight based on a total weight of the resins (B) and (C) fromthe standpoints of weather resistance, stain resistance, etc.

The resin 2 may include, if needed, the hydroxyl group-containing resin(A).

Resin 3:

The resin 3 may preferably have one or more on an average, preferably 2to 40 on an average of silanol group and/or hydrolyzable silyl group inone molecule, one or more on an average, preferably 2 to 40 of epoxygroup in one molecule, and 2 to 200 on an average of hydroxyl group inone molecule from the standpoints of weather resistance, stainresistance, etc.

The resin 3 may preferably include, for example, a copolymer of thehydroxy group-containing polymerizable unsaturated monomer (h), theepoxy group-containing polymerizable unsaturated monomer (j), the silanecompound (k-1) and/or the macromonomer (k-2) and, if needed, otherpolymerizable unsaturated monomer (i).

A mixing ratio of the monomers (h), (j), (k-1) and (k-2) may be suchthat respective functional groups in the resin are within the aboveranges.

The resin 3 may desirably have a number average molecular weight of1,000 to 100,000, preferably 3,000 to 60,000.

The resin 3 may include, if needed, the hydroxyl group-containing resin(A). Of the above resins 1 to 3, the resin 3 is preferred from thestandpoints of weather resistance and stain resistance.

The curing catalyst used in the above coating composition is used forpromoting reactions of silanol group, hydrolyzable silyl group, epoxygroup, and hydroxyl group in the base resin, and may preferably includemetal alkoxides obtained by bonding alkoxy group to metals such asaluminium, titanium, zirconium, calcium, barium and the like; metalchelate compounds obtained by coordinating a chelate compound capable ofconstituting a keto-enol isomer with the above metal alkoxides; Lewisacids such as Al Cl₃, Al (C₂ H₅)₂ Cl , TiCl₄, ZrCl₄, SnCl₄, FeCl₃, BF₃,BF₃ : (OC₂ H₅)₂ and the like; protonic acids including organic protonicacids such as methanesulfonic acid, benzene-sulfonic acid,p-toluenesulfonic acid and the like, and inorganic protonic acids suchas phosphoric acid, phosphorous acid, phosphinic acid, sulfuric acid andthe like; compounds having Si-O-Al linkage such as aluminium silicate;and the like. Of these, the metal thelate compound is preferred, and maypreferably include aluminium thelate compounds such as diisopropoxyethylacetoacetate aluminium, tris (ethylacetoacetate) aluminium, isopropoxy.bis(ethylacetoacetate) aluminium,monoacetylacetonato.bis(ethylacetoacetate) aluminium, tris(n-proylacetoacetate) aluminium, tris(n-butylacetoacetate) aluminium,monoethylacetoacetate.bis(acetylacetonato), aluminium,tris(acctylacetonato) aluminium, tris(propionylacetonato) aluminium,acetylacetonato.bis(propionylacetonato) aluminium and the like; titaniumchelate compounds such as diisopropoxy.bis(ethylacetoacetate) titanium,diisopropoxy.bis(acetylacetonato) titanium and the like; zirconiumchelate compounds such as tetrakis (n-propylacetoacetate) zirconium,tetrakis (acetylacetonato) zirconium, tetrakis (ethylacetoacetate)zirconium and the like; and the like.

A mixing amount of the curing catalyst is 0.01 to 30 parts by weight,preferably 0.1 to 10 parts by weight per 100 parts by weight of the baseresin. When the amount of the curing catalyst is less than 0.01 part byweight, weather resistance and stain resistance are undesirably reduced.When more than 30 parts by weight, water resistance of the film isundesirably reduced.

The organic solvent used in the reactively curable coating compositionmay include conventionally used organic solvents which are substantiallyinactive to the curable resin composition and capable of dissolving ordispersing the curable resin composition. Specific examples of theorganic solvent may include aromatic hydrocarbon solvents such astoluene, xylene and the like, ketones such as methyl ethyl ketone,methyl isobutyl ketone and the like, esters such as ethyl acetate, butylacetate and the like, ethers such as dioxane, ethyleneglycol diethylether and the like, alcohols such as butanol, propanol and the like,aliphatic hydrocarbons such as pentane, hexane, heptane and the like,and the like.

A mixing ratio of the organic solvent is in the range of about 10 to 95%by weight, preferably about 20 to 90% by weight based on a total weightof the solvent and the curable resin composition.

In addition to the above reactively curable coating composition, thesolvent based organic coating composition may include non-crosslinkablecoating composition.

The non-crosslinkable coating composition is a solvent based ordispersible organic solvent based coating composition which is such thatthe solvent evaporates at room temperature or by heating to form a film.

The non-crosslinkable coating composition is such that after theresulting film has been treated with acid, the film surface shows acontact angle to water of 70° or less.

The non-crosslinkable coating composition is not particularly limited solong as the above conditions are satisfied, and may includeconventionally used ones. Specific examples may include cellulosederivative coating composition such as nitrocellulose lacquer, acetylcellulose lacquer, acetylbutyl cellulose lacquer, ethyl celluloselacquer and the like, acrylic resin based coating composition, urethaneresin based coating composition, vinyl chloride resin coatingcomposition, fluorocarbon resin based coating composition, alkyd resinbased coating composition, vinyl acetate resin based coatingcomposition, styrene-butadiene resin based coating composition, vinylchloride organosol coating composition and the like.

The organic solvent may arbitrarily be selected depending on a kind ofthe coating composition, and specifically includes, for example,hydrocarbons such as hexane, heptane and the like, alcohols such aspropanol, butanol and the like, ethers such as ethyl cellosolve, butylcellosolve, diethylene glycol monoethyl ether and the like, ketones suchas acetone, methyl ethyl ketone, methyl isobutyl ketone and the like,esters such as ethyl acetate, propyl acetate, butyl acetate, cellosolveacetate and the like, and the like.

A content of the organic solvent is about 10 to 95% by weight,preferably about 20 to 90% by weight.

The water based coating composition may include conventionally usedones, for example, curable or non-curable ones, water-soluble, waterdispersible or emulsifiable ones, and anionic, cationic or nonionicones. Specifically, the kind of the coating composition depending on thebase resin may include, for example, alkyd resin based, polyester resinbased, silicone resin based, fluorocarbon resin based, epoxy resinbased, urethane resin based, acrylic resin based, vinyl chloride resinbased, vinyl acetate resin based, polybutadiene resin based and theirmodified resins based coating compositions. The above curable coatingcomposition may include, for example, amino-curable ones, (blocked)polyisocyanate-curable ones, oxidative polymerization-curable ones,actinic ray-curable ones, and the like.

The water based coating composition to be used is such that a filmsurface, which has been treated with acid, shows a contact angle towater of 70° or less.

The liquid coating composition free of the organic solvent or water mayinclude cross linkable or non-crosslinkable, solution type or dispersiontype, organic solvent-free liquid. coating compositions, and mayspecifically include, for example, an actinic ray-curable coatingcomposition, vinyl chloride plastisol coating composition and the like.

Formation of a film by use of the liquid coating composition may becarried out, for example, by irradiating the actinic ray such asultraviolet light, electron beam and the like in the case where theactinic ray-curable coating composition is used, or by heating in thecase where the vinyl chloride plastisol coating composition is used.

The powder coating composition may include conventionally usedheat-curable powder coating composition which contain powdered curableresin composition as a resin component and is capable of beingreactively cured by itself to form a crosslinked film structure.

The powder coating composition is such that a surface of a finallyformed cured film, which has been treated with acid, shows a contactangle to water of 70° or less.

The powdered curable resin composition may generally include onesobtained, for example, by incorporating a curing agent to react with afunctional group in the powdered curable resin into the powdered curableresin having the functional group. Examples of the functional group inthe powdered curable resin may include hydroxyl group, carboxyl group,epoxy group and the like Examples of the powdered curable resin mayinclude acrylic resin, polyester resin, silicone resin, fluorocarbonresin and modified resins thereof such as silicone-modified acrylicresin.

Examples of the curing agent may include polycarboxylic acid such asazelaic acid, sebacic acid, dodecanoic diacid and the like, blockedpolyisocyanate such as isophorone diisocyanate blocked withε-caprolactam, polyepoxide such as triglycidyl isocyanurate, and thelike.

Of these, the powdered curable resin composition may preferably includeacrylic curable resin composition such as one containing, as thepowdered curable resin, glycidyl group-containing acrylic resincontaining glycidyl (meth)acrylate as a comonomer and polycarboxylicacid, dodecane diacid as a curing agent, and one containing, as thepowdered curable resin, hydroxyl group-containing acrylic resincontaining hydroxyethyl (meth)acrylate and blocked polyisocyanate as acuring agent; and polyester curable resin composition containingcarboxyl group-containing polyester resin as the powdered curable resinand polyepoxide such as triglycidyl lsocyanurate as a curing agent fromsuch standpoints as to be improved in Weather resistance and stainresistance and to be available at relatively lower cost composed withcurable resin composition such as silicone based ones, fluorine basedones and the like.

The organosilicate used in the topcoating composition of the presentinvention includes ones represented by the general formula: ##STR3##where R is same or different and is hydrogen atom or a monovalenthydrocarbon group having 1 to 10 carbon atoms and its condensates. Useof such an organosilicate as to have a carbon number more than 10 in Rresults in reducing a speed of hydrolysis and in making poor the stainresistance and durability of the film.

Examples of the monovalent hydrocarbon group having 1 to 10 carbon atomsin the above general formula may include alkyl group, aryl group and thelike.

The above "alkyl group" may include straight-chain ones and branchedones, for example, methyl, ethyl, n-propyl, iso-propyl, n-butyl,iso-butyl, tert-butyl, n-pentyl, iso-pentyl, neopentyl, n-hexyl,iso-hexyl, n-octyl and the like. Of these, lower alkyl groups having 1to 3 carbon atoms are preferred. The "aryl group" may include monocyclicand polycyclic ones, for example, phenyl group, toluyl group, xylylgroup, naphtyl group and the like, phenyl group being preferred.

Preferable examples of the organosilicate used in the present inventionmay include tetrahydroxysilane, tetramethoxysilane, tetraethoxysilane,tetrapropoxysilane, tetrabutoxysilane, tetraphenoxysilane,dimethoxydiethoxysilane and the like. These may be used alone or incombination.

The condensate of organosilicate may include branched or straight-chaincondensates between organosilicates represented by the above generalformula and preferably includes condensater having a degree ofcondensation of 2 to 100 and represented by the general formula:##STR4## where R is defined as above, n is an integer of 2 to 100.

In the above general formula, when n is more than 100, effect of stainresistance is undesirably reduced.

The organosilicate used in the present invention may preferably includesuch ones that R in the general formula is a lower alkyl group having 1to 3 carbon atoms, and the condensate thereof may particularly includesuch ones that R in the general formula is a lower alkyl group having 1to 3 carbon atoms and that the degree of condensation is in the range of2 to 10.

A mixing ratio of the organosilicate or the condensate thereof is in therange of about 0.1 to 50 parts by weight, preferably about 1 to 40 partsby weight per 100 parts by weight of a resin solid content in the abovecoating composition. When the amount of the organosilicate or thecondensate thereof is less than about 0.1 part by weight, the film showsundesirably poor stain resistance. On the other hand, when more thanabout 50 parks by weight, the film may be hardened and may undesirablyresult defects such as cracking, reduction in gloss and the like.

In addition to the above, the topcoating composition of the presentinvention may include, if needed, colorants, fillers, flow modifiers,plasticizers, curing catalysts, ultraviolet light absorbents, resinsother than the above such as trialkoxysilane, dialkoxysilane,monoalkoxysilane, lower condensates thereof and the like, and the like.

The topcoating composition of the present invention is such that thesurface of the finally formed cured film is treated with acid, so thatthe resulting film surface may have a contact angle to water of 70° orless, preferably 20° to 65°. The contact angle is a value obtained bysuch a manner that a coated film immediately after curing is dipped andtreated with a 25 wt % aqueous sulfuric acid solution at 20° C. for 24hours, followed by washing an aqueous sulfuric acid solution adheredonto the film with water, drying, dropping a 0.03 cc deionized waterdrop onto the film surface, and by measuring a contact angle to water ofthe water drop 3 minutes after at 20° C. by use of a contact angle meterDCAA marketed by Kyowa Chemical Co., Ltd. When the contact angle is morethan 70°, stain resistance and durability become poor.

According to the topcoating composition of the present invention, theabove topcoating composition is coated onto a substrate, followed byforming a cured film at room temperature or by heating. When exposedoutdoors, a contact angle to water of the film surface is slowly reduceddue to an acid ingredient such as an acid rain, and the film surface isprevented from being stained.

According to the present invention, it is preferred that the film istreated with an acid beforehand prior to being exposed outdoors. Theprior acid treatment results in making it possible to prevent stain ofthe film surface from the beginning.

The substrate to coat the above topcoating composition may broadlyinclude inorganic substrates such as glass, slate, concrete and thelike; metal substrates, for example, metals such as aluminium, steel,tin, copper, stainless steel and the like, such metals as to be obtainedby plating zinc, tin, chromium, etc. onto a surface of steel, and suchmetals as to treat a surface of steel, etc. with chromic acid,phosphoric acid, etc.; plastic substrates such as polyethylene,polyvinyl chloride, ABS and the like; tapes obtained by applying anadhesive or pressure-sensitive adhesive onto a substrate film such aspolyvinyl chloride, polyethylene terephtharate, aluminium and the like;substrates obtained, if needed, by coating a known primer, intercoatingcomposition and topcoating composition onto the above substrates, andthe like.

The coating method of the topcoating composition may be carried out bycoating the topcoating composition onto the surface of the substrate bymeans of, for example, brushing, spray coating, roller coating, dipcoating, electrostatic powder coating, etc. A coating thickness may varydepending on the kind of the coating composition, coating means, etc.,but generally in the range of about 1 to 500 μm, preferably about 10 to100 μm. A drying conditions of the film may be selected depending on thekind of the topcoating composition. For example, in the case where atopcoating composition, which contains a metal chelate compound and abase resin containing hydrolyzable silyl group, hydroxyl group and epoxygroup as the essential functional group components, is used, the dryingconditions are at room temperature for about 24 hours or at about 140°C. for about 20 minutes when heated; in the case where a topcoatingcomposition containing a hydroxyl group-containing resin as the baseresin and a polyisocyanate compound as the crosslinking agent is used,the drying conditions are at room temperature for about 8 hours; in thecase where a topcoating composition containing a hydroxylgroup-containing resin as the base resin and a blocked polyisocyanatecompound or amino resin as the crosslinking agent is used, the dryingconditions are at about 140° C. for about 30 minutes; and in the casewhere a powder coating composition is used, the drying conditions aregenerally at about 140° C. to 300° C. for about 10 seconds to about 60minutes.

The acid treatment of the film is carried out to such an extent that thefilm surface shows a contact angle to water of 70° or less, preferably20° to 65° the method of the acid treatment may not particularly belimited so long as the above conditions are satisfied, but specificallythe film may preferably be treated in an acidic aqueous solution havinga pH of 6 or less at about 5° C. to 98° C. Examples of particularlypreferable acids to be used may include inorganic acids such as sulfuricacid, hydrochloric acid, nitric acid, phosphoric acid and the like.Preferably, the acidic aqueous solution adhered onto the treated film isremoved. The contact angle may be measured in the same manner as abovedescribed.

FUNCTION AND EFFECT OF THE INVENTION

The topcoating composition of the present invention provides remarkableeffects on retension of stain resistance and durability compared withthe method of coating an organic solvent solution of alkylsilicate ontothe surface of the molded product, and the method of incorporatingalkylsilicate into a thermoplastic resin as in the prior art. Reasonsthereof are not clear, but are considered as follows.

The conventional film formed by the organic solvent solution ofalkylsilicate may show defects such as crazing, cracking, shrinking andthe like, because the alkylsilicate itself has poor film-formingproperties, resulting in that when exposed outdoors the film may bepeeled off the substrate due to the external factors such as rain, sun,heat, dust and the like to lose effect of stain resistance. It may alsobe possible to reduce defects such as crazing to a minimum by making afilm thickness thinner, but it is difficult for this case to maintainthe above effect for a long period of time, because the film is abradedby dust, etc. during exposure to outdoors.

Contrary thereto, it is guessed that since the topcoating composition ofthe present invention consists of the above components and the filmtherefrom has a contact angle to water of 70° or less, the film is suchthat a layer rich in the organosilicate or its condensate film componentis formed in a film surface layer or in its neighborhood and a layerrich in an organic film is formed in the interior of the film, resultingin that the organosilicate or its condensate film component isreinforced by the organic film to improve retension of stain resistanceand durability.

The method of incorporating alkylsilicate into thermoplastic resin hassuch disadvantages that then a large amount of alkylsilicate isincorporated, characteristics of the thermoplastic resin is lost and thefilm may show poor fabrication quality, etc., on the other hand, when anamount of the organosilicate to be incorporated is controlled to such anextent that the fabrication quality is maintained, it is impossible toobtain a film showing good stain resistance, without satisfyingrequirements of both fabrication quality and stain resistance.

Contrary thereto, the topcoating composition of the present invention issuch that the film formed therefrom comprises the surface layer rich inorganosilicate or its condensate and the interior layer rich in theorganic film as above described, and requirements of stain resistanceare satisfied by the presence of organosilicate or its condensate andrequirements of durability, fabrication quality, adhesion properties,etc. are satisfied by the presence of the organic film, resulting inproviding remarkable effects to satisfy requirements of both stainresistance and durability.

Moreover, the film formed according to the process of the presentinvention is such that the layer rich in organosilicate or itscondensate is formed in the film surface layer or in its neighborhood,and the organosilicate or its condensate therein is condensated and ismade high-molecular weight, resulting providing effects to show goodproperties in stain resistance and durability from the beginning.

Industrial Applicability

The topcoating composition and film-forming process according to thepresent invention are useful for coating of outdoor substrates such asbuilding structures, displays, guard fences, instruments, machines andthe like.

EXAMPLE

The present invention will be explained more in detail by the followingExamples, in which "part" and "%" are by weight basis.

Reactively Curable Organic Solvent Based Coating Composition

Reactively Curable Resin Composition 1

A reactively curable resin composition 1 was prepared by incorporatingone part of tris (acetylacetonato) aluminium into 200 parts of a resinhaving a resin solid content of 50% and a number average molecularweight of 40,000, and obtained by radically polymerizing in xylene amixture of 100 parts of γ-methacryloxypropyl-trimethoxaysilane, 14.2parts of glycidyl methacrylate, 12.0 parts of 2-hydroxyethylmethacrylate, 63.8 parts of n-butyl methacrylate and 2 parts ofazobisisobutylvaleronitride.

Reactively Curable Resin Composition 2

A mixture of 5 parts of γ-methacryloxypropyltrimethoxysilane, 95 partsof methyltrimethoxysilane, 30 parts of deionized water and 98% formicacid was reacted at 100° C. for 8 hours to obtain a siloxanemacromonomer having a number average molecular weight of 2,500.

Next, one part of tris (acetylacetonato) aluminium was incorporated into200 parts of a resin having a resin solid content of 50% and a numberaverage molecular weight of 8,000, and obtained by radicallypolymerizing a mixture of 15 parts of the siloxane macromonomer, 20parts of 3,4-epoxycyclohexyl methacrylate, 18 parts of 2-hydroxyethylacrylate, 32 parts of n-butyl methacrylate, 15 parts of styrene and 4parts of azobisisobutylonitrile in isobutyl acetate to obtain areactively curable resin composition 2.

Reactively Curable Resin Composition 3

RETAN 1026 CLEAR (Trademark, marketed by Kansai Paint Co., Ltd.,acrylopolyisocyanate-curable organic solvent based coating composition,resin solid content: 50%)

Reactively Curable Resin Composition 4

KANPE-FRON CW CLEAR (Trademark, marketed by Kansai Paint Co., Ltd.,Fluoropolyisocyanate-curable organic solvent based coating composition,resin solid content: 50%)

Reactively Curable Resin Composition 5

KANPE-FRON 160 CLEAR (Trademark, marketed by Kansai Paint Co., Ltd.,fluoro amino-curable organic solvent based coating composition, resinsolid content: 50%)

Examples 1-14

Topcoating compositions of Examples 1-14 were obtained according toformulations based on solid content as listed in Table 1 respectively.

Comparative Examples 1-5

Comparative topcoating compositions of Comparative Examples 1-5 wereobtained according to formulations as listed in Table 1 respectively.

Preparation of Coated Plate

KANPE CURE PRASAF #500 IVORY (Trademark of epoxy resin basedundercoating composition, marketed by Kansai Paint Co., Ltd. was coatedonto a 0.8 mm thick steel plate treated with zinc phosphate to be a dryfilm thickness of 20 μm, followed by drying, coating KANPE-FRON CW(Trademark of fluorine based white topcoating composition, marketed byKansai Paint Co., Ltd.) to be a dry film thickness of 20 μm, and bydrying to obtain a substrate.

Next, the surface of the substrate was slightly abraded, followed bycoating thereonto topcoating compositions of Examples and comparativetopcoating compositions of Comparative Examples to be a dry filmthickness of 20 μm by use of the bar coater respectively, and by dryingunder the conditions shown in Table 1 to obtain coated platesrespectively.

Results of film performance tests are shown in Table 1.

                                      TABLE 1                                     __________________________________________________________________________                 Examples                                                                      1   2  3   4   5   6   7   8   9                                 __________________________________________________________________________    Formulations                                                                  Curable resin composition                                                     kind         1                              2                                 amount       100                                                              organo silicates                                                              tetraphenyl silicate                                                                           10                                                           tetraethyl silicate                                                                        20     40                      20                                tetraphenylethyl silicate                                                                             10                                                    methyl silicate 51(*1)      10                                                ethyl silicate 40(*1)           20  30                                        ethyl silicate 48(*3)                   20                                    Drying conditions                                                                          20° C.                                                                     140° C. - 30 minutes                                               24 hrs                                                           Contact angle to water(*4)                                                                 61°                                                                        62°                                                                       57°                                                                        62°                                                                        62°                                                                        58°                                                                        59°                                                                        59°                                                                        60°                        Film appearance prior to                                                                   ⊚                                                                  ⊚                                                                 ⊚                                                                  ⊚                                                                  ⊚                                                                  ⊚                                                                  ⊚                                                                  ⊚                                                                  ⊚                  outdoor exposure(*5)                                                          Outdoor exposure tests(*6)                                                    3 months                                                                      gloss retension                                                                            100 100                                                                              100 100 100 100 100 100 100                               color difference                                                                           2.9 3.2                                                                              1.2 3.3 3.4 1.8 1.5 1.8 2.8                               appearance   ⊚                                                                  ⊚                                                                 ⊚                                                                  ⊚                                                                  ⊚                                                                  ⊚                                                                  ⊚                                                                  ⊚                                                                  ⊚                  6 months                                                                      gloss retension                                                                            100 99 100 100 99  100 100 100 100                               color difference                                                                           2.4 3.0                                                                              1.1 3.1 3.3 1.5 1.3 1.3 2.3                               appearance   ⊚                                                                  ⊚                                                                 ⊚                                                                  ⊚                                                                  ⊚                                                                  ⊚                                                                  ⊚                                                                  ⊚                                                                  ⊚                  12 months                                                                     gloss retension                                                                            100 96 100 96  97  99  100 100 100                               color difference                                                                           2.1 2.8                                                                              1.0 2.9 3.0 1.0 1.0 1.0 1.9                               appearance   ⊚                                                                  ⊚                                                                 ⊚                                                                  ⊚                                                                  ⊚                                                                  ⊚                                                                  ⊚                                                                  ⊚                                                                  ⊚                  Adhesion properties(*2)                                                                    ◯                                                                     ◯                                                                    ◯                                                                     ◯                                                                     ◯                                                                     ◯                                                                     ◯                                                                     ◯                                                                     ◯                     Fabricating properties(*3)                                                                 30  30 30  30  30  30  30  30  30                                __________________________________________________________________________                 Examples       Comparative Examples                                           10 11 12 13 14 1  2  3  4  5  6                                  __________________________________________________________________________    Formulations                                                                  Curable resin composition                                                     kind         2  3  4  5  5  1  2  3  4  5  tetraethyl                         amount       100                           silicate                           organo silicates                                                              tetraphenyl silicate                                                          tetraethyl silicate                                                                           20                                                            tetraphenylethyl silicate                                                     methyl silicate 51(*1)                                                        ethyl silicate 40(*1)                                                                      20                                                               ethyl silicate 48(*3)                                                         Drying conditions                                                                          140° C. - 30 minutes                                                                  140° C. - 30 minutes                                                                  20° C.                                                                 24 hrs                             Contact angle to water(*4)                                                                 59°                                                                       66°                                                                       67°                                                                       68°                                                                       61°                                                                       85°                                                                       88°                                                                       82°                                                                       88°                                                                       90°                                                                       **                                 Film appearance prior to                                                                   ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ◯                      outdoor exposure(*5)                                                          Outdoor exposure tests(*6)                                                    3 months                                                                      gloss retension                                                                            100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                color difference                                                                           1.8                                                                              6.0                                                                              6.9                                                                              6.9                                                                              2.5                                                                              7.0                                                                              7.0                                                                              7.0                                                                              8.0                                                                              8.1                                   appearance   ⊚                                                                 ◯                                                                    ◯                                                                    ◯                                                                    ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ◯                      6 months                                                                      gloss retension                                                                            100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              99 100                                                                              99 100                                                                              100                                   color difference                                                                           1.4                                                                              5.2                                                                              5.3                                                                              5.5                                                                              1.5                                                                              5.5                                                                              6.0                                                                              7.5                                                                              9.0                                                                              9.2                                   appearance   ⊚                                                                 ◯                                                                    ◯                                                                    ◯                                                                    ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 X                                  12 months                                                                     gloss retension                                                                            99 95 95 100                                                                              100                                                                              96 98 90 100                                                                              100                                   color difference                                                                           1.0                                                                              4.8                                                                              4.9                                                                              4.7                                                                              1.0                                                                              4.8                                                                              5.2                                                                              8.3                                                                              11.0                                                                             11.5                                  appearance   ⊚                                                                 ◯                                                                    ◯                                                                    ◯                                                                    ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 X                                  Adhesion properties(*2)                                                                    ◯                                                                    ◯                                                                    ◯                                                                    ◯                                                                    ◯                                                                    ◯                                                                    ◯                                                                    ◯                                                                    ◯                                                                    ◯                                                                    --                                 Fabricating properties(*3)                                                                 30 30 30 30 30 30 30 30 30 30 --                                 __________________________________________________________________________     In Table 1, (*1) to (*3) means as follows respectively.                       (*1)Methyl silicate 51, ethyl silicate 40 and ethyl silicate 48:              Trademarks of lower condensates of tetraalkyl silicate, marketed by           Colcote Co., Ltd.                                                             (*2)Adhesion properties: A test was made according to the cross cut tape      test defined in JIS K5400 8.5.2., by forming 100 (1 × 1 mm) squares     followed by adhering thereonto an adhesive cellophane tape, separating th     tape, and by examining a number of remaining squares. Evaluation was made     as follows: ◯ shows that none of the squares was peeled off,      Δ shows that some corners of the squares were peeled off, an X show     that one third of the squares were peeled off.                                (*3)Fabricating properties: Tests were carried out by use of Du pont          impact tester under the conditions of a radius from an impact center of       1/2 inch and a falling weight of 500 g. A maximum height developing no        cracks on the film surface is shown.                                          (*4)Contact angle to water: It shows a value obtained by such a measuring     method that a film immediately after being formed is dipped into a 25 wt      aqueous sulfuric acid solution to be treated at 20° C. for 24 hour     followed by washing the aqueous sulfuric acid solution adhered onto the       film with water, drying, dropping a 0.03 cc water drop of deionized water     onto the surface of the film, and measuring a contact angle of the water      drop three minutes after at 20° C. by use of  a Contactangle meter     DCAA marketed by Kyowa Chemical Co., Ltd. In Table 1, ** shows that           measurements were impossible due to elution.                                  (*5)Appearance: The surface of the film was examined by the naked eye to      evaluate as follows.                                                          ⊚: The film shows no defects such as crazing, flashing,        flaking and the like.                                                         ◯: The film shows a little development of crazing and             flashing.                                                                     Δ: The film shows some development of crazing, flashing and flaking     X: The film shows a remarkable development of crazing, flashing and           flaking.                                                                      (*6)Gloss retension: Showing a value calculated and obtained by the           following equation: (60° specular reflection percentage after          outdoor exposure)/(60° specular reflection percentage prior to         outdoor exposure) × 100. Color difference: Showing a color              difference between before and after exposure as ΔE.sub.ab in            accordance with JIS Z8730. Appearance: Evaluated in the same manner as in     (*5).                                                                    

In Example 14, a film immediately after being formed was dipped into a2.5 wt % aqueous sulfuric acid solution to be treated at 20° C. for 24hours, followed by washing the aqueous sulfuric acid solution adheredonto the film surface with water, and by drying to be used for tests ofoutdoor exposure tests, adhesion properties and fabricating properties.In connection therewith, in Examples other than this Example andComparative Examples, a film not treated as above was used.

Non-crosslinkable organic solvent based coating composition

FUCARON (white): Trade name of fluorocarbon resin based coatingcomposition, resin solid content of 32%, marketed by Kansai Paint Co.,Ltd.

ACRIC 2000 GL (white): Trade name of acrylic resin based coatingcomposition, resin solid content of 30%, marketed by Kansai Paint Co.,Ltd.

VINYBON 100 (white): Trade name of vinyl chloride resin based coatingcomposition, resin solid content of 27%, marketed by Kansai Paint Co.,Ltd.

MULTI-TILE OVER COAT AC (white): Trade name of vinyl acetate-acrylicresin based coating composition, resin solid content of 25%, marketed byKansai Paint Co., Ltd.

KP COLOR 4009 (white): Trade name of vinyl chloride sol resin coatingcomposition, resin solid content of 85%, marketed by Kansai Paint, Co.,Ltd.

Solvent-free coating composition

ZONNE OVER COAT W-2000 CLEAR: Trade name of urethane acrylate resinbased ultraviolet light-curable coating composition, resin solid contentof 100%, marketed by Kansai Paint Co., Ltd.

Examples 15-25

Non-crosslinkable or solvent-free coating compositions, organosilicatesand their condensates were formulated as shown in Table 2 to obtainrespective coating compositions of Examples 15-25. In Table 2, theformulation shows parts by weight of organosilicate and its condensateper 100 parts by weight of the resin solid content in the coatingcomposition.

Comparative Examples 6-11

Non-crosslinkable or solvent-free coating compositions in Table 2 wereused as comparative coating compositions respectively.

                                      TABLE 2                                     __________________________________________________________________________                Examples                         Comparative Examples                         15 16 17 18 19 20 21 22 23 24 25 6  7  8  9  10 11                __________________________________________________________________________    Coating Compositions                                                          Non-crosslinkable                                                             FUCA RON (white)                                                                          100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100               100                              ACRIC 2000 GL                 100               100                           (white)                                                                       VINYBON 100 (white)              100               100                        MULTIL-TILE OVER                    100               100                     COAT AC (white)                                                               KP COLOR 4009                          100               100                  (white)                                                                       solvent-free                                                                  ZONNE OVER COAT                           100               100               SW-2000 CLEAR                                                                 Organo silicates and                                                          thier condensates                                                             tetraphenyl silicate                                                                       20                      20                                       tetraethyl silicate                                                                           10             20                                             tetrapnylethyl silicate                                                                          20             20                                          methyl silicate 51*   20                                                      ethyl licate 40*         20             20                                    ethyl licate 48*            20             20                                 __________________________________________________________________________     *Methyl silicate 51, ethyl silicates 40 and 48 are trademarks of lower        iondensates of tetraalkyl silicate, marketed by Colcote Co., Ltd.             (hereinafter referred to as such)                                        

Film appearance and performances:

Results are shown in Table 3.

Preparation of coated test plates:

Examples 15-24 and Comparative Examples 6-10

KANPE CURE PRASAF 500 IVORY (Trade name of epoxy resin based undercoatcoating composition, marketed by Kansai Paint Co., Ltd.) was coated ontoa zinc phosphate-treated steel plate (0.8 mm in thickness) to be a dryfilm thickness of 20 μm, followed by drying, coating thereonto coatingcompositions corresponding to Examples and Comparative Examplesrespectively, and by evaporating an organic solvent at room temperatureor by heating to obtain coated test plates corresponding to Examples andComparative Examples respectively.

Example 25 and Comparative Example 11

KANPE CURE PRASAF 500 IVORY (Trade name of epoxy resin based undercoatcoating composition, marketed by Kansai Paint Co., Ltd.) was coated ontoa zinc phosphate-treated steel plate (0.8 mm in thickness) to be a dryfilm thickness of 20 μm, followed by drying, coating thereonto RETAN1026 WHITE (Trade name of acrylic polyisocyanate resin based coatingcomposition, marketed by Kansai Paint Co., Ltd.) to be a dry filmthickness of 20 μm, drying, coating thereonto coating compositionscorresponding to Examples and Comparative Examples, and by irradiatingultraviolet light for curing, resulting in obtaining coated test platescorresponding to Examples and Comparative Examples.

In Table 3, (*2) to (*6) have the same meanings as above.

Treatment (*7) in Table 3: A resulting film was dipped into a 2.5 wt %aqueous sulfuric acid solution at 20° C. for 24 hours, followed bywashing the aqueous sulfurin acid solution adhered onto the film withwater, and by drying at room temperature to be referred to as "treated".On the. other hand, a case where the above treatment was not carried outis referred to as "non-treated".

                                      TABLE 3                                     __________________________________________________________________________             Examples                            Comparative Examples                      15    16 17 18 19 20 21 22 23 24 25 6  7  8  9  10 11                __________________________________________________________________________    Treatment(*7)                                                                          non-                                                                             trea-                                                                            non-                                                                             non-                                                                             non-                                                                             non-                                                                             non-                                                                             non-                                                                             non-                                                                             non-                                                                             non-                                                                             non-                                                                             non-                                                                             non-                                                                             non-                                                                             non-                                                                             non-                                                                             non-                       trea-                                                                            ted                                                                              trea-                                                                            trea-                                                                            trea-                                                                            trea-                                                                            trea-                                                                            trea-                                                                            trea-                                                                            trea-                                                                            trea-                                                                            trea-                                                                            trea-                                                                            trea-                                                                            trea-                                                                            trea-                                                                            trea-                                                                            trea-                      ted   ted                                                                              ted                                                                              ted                                                                              ted                                                                              ted                                                                              ted                                                                              ted                                                                              ted                                                                              ted                                                                              ted                                                                              ted                                                                              ted                                                                              ted                                                                              ted                                                                              ted                                                                              ted               Contact angle to                                                                       56    62 61 59 58 60 61 59 60 57 58 92 89 89 90 90 89                water(*4)                                                                     Film appearance                                                                        ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                              4  .circleincircl                                                                e.                prior to outdoor                                                              exposure(*5)                                                                  Outdoor exposure                                                              test(*6)                                                                      1 month                                                                       gloss retension                                                                        100                                                                              100                                                               color difference                                                                       5.8                                                                              2.8                                                               appearance                                                                             ⊚                                                                 ⊚                                                  3 months                                                                      gloss retension                                                                        100                                                                              100                                                                              100                                                                              99 100                                                                              99 100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              99 99 100                                                                              98 100               color difference                                                                       3.5                                                                              2.7                                                                              2.9                                                                              3.1                                                                              3.2                                                                              3.5                                                                              3.8                                                                              3.2                                                                              3.4                                                                              2.8                                                                              2.9                                                                              2.4                                                                              7.9                                                                              8.5                                                                              8.1                                                                              7.2                                                                              7.3                                                                              7.6               appearance                                                                             ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 .circleincircl                                                                e.                __________________________________________________________________________

Water-based coating composition

VINY-DELUXE 300 (white): Trade name of acrylic resin emulsion coatingcomposition, marketed by Kansai Paint Co., Ltd.

ASCA (white): Trade name of self-crosslinking acrylic resin water-basedcoating composition. ALES-GUMTEX (white): Trade name of acrylic rubberlater, marketed by Kansai Paind Co., Ltd.

Acrylic melamine (white): A water dispersion of acrylic resin having ahydroxyl value of 100 and an acid value of 60, butylated melamine resin,resin solid content weight ratio between the former resin to the latterresin being 60 to 20, diethanolamine in a neutralization equivalent of0.8 and titanium white in an amount of 80 parts by weight per 100 partsby weight of the resin.

Examples 26-34

Water-based coating compositions and organosilicates and theircondensates as shown in Table 4 were formulated to obtain respectivecoating compositions of Examples 26-32. In Table 4, the aboveformulations are represented by parts by weight of organosilicates andtheir condensates per 100 parts by weight of the resin solid content inthe water-based coating composition.

Comparative Examples 12-15

Water-based coating compositions shown in Table 4 were used ascomparative coating compositions of Comparative Examples 12-15respectively.

                                      TABLE 4                                     __________________________________________________________________________                      Examples                   Comparative Examples                               26 27 28 29 30 31 32 33 34 12 13 14 15                      __________________________________________________________________________    Water-based coating compositions                                              VINY-DELUXE 300 (white)                                                                         100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100         100                              ASCA (white)                        100         100                           ALES-GUMTEX (white)                    100         100                        Acrylic melamine (white)                  100         100                     Organo silicates and their condensates                                        tetraphenyl silicate                                                                             20                      20                                 tetraethyl silicate   10             20                                       tetraphenylethyl silicate                                                                              20             20                                    methyl silicate 51(*)       20                                                ethyl silicate 40(*)           20                                             ethyl silicate 48(*)              20                                          __________________________________________________________________________

Film appearance and performances: Results are shown in Table 5.

Preparation of coated test plates:

Examples 26-34 and Comparative Examples 12-15

KANPE CURE PRASAF 500 IVORY (Trade name of epoxy resin based undercoatcoating composition, marketed by Kansai Paint Co., Ltd.) was coated ontozinc phosphate-treated steel plate (0.8 mm in thickness) to be a dryfilm thickness of 20 μm, followed by drying, coating thereonto coatingcompositions corresponding to Examples and Comparative Examplesrespectively, and by drying at room temperature, i.e. 20° C. for 24hours when VINY-DELUXE 300, ASCA and ALES-GUMTEX are used, or by heatingand drying at 180° C. for 20 minutes when acrylic melamine is used toobtain coated test plates corresponding to Examples and ComparativeExamples respectively.

In Table 5, (*4)-(*7) have the same meanings as above.

                                      TABLE 5                                     __________________________________________________________________________                    Examples                      Comparative Examples                            26    27 28 29 30 31 32 33 34 12 13 14 15                     __________________________________________________________________________    Treatment(*7)   non-                                                                             trea-                                                                            non-                                                                             non-                                                                             non-                                                                             non-                                                                             non-                                                                             non-                                                                             non-                                                                             non-                                                                             non-                                                                             non-                                                                             non-                                                                             non-                                   trea-                                                                            ted                                                                              trea-                                                                            trea-                                                                            trea-                                                                            trea-                                                                            trea-                                                                            trea-                                                                            trea-                                                                            trea-                                                                            trea-                                                                            trea-                                                                            trea-                                                                            trea-                                  ted   ted                                                                              ted                                                                              ted                                                                              ted                                                                              ted                                                                              ted                                                                              ted                                                                              ted                                                                              ted                                                                              ted                                                                              ted                                                                              ted                    Contact angle to water(*4)                                                                    66    65 62 63 66 65 60 63 64 89 90 90 89                     Film appearance prior to outdoor                                                              ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚       exposure(*5)                                                                  Outdoor exposure tests(*6)                                                    one month                                                                     gloss retension 100                                                                              100                                                        color difference                                                                              6.8                                                                              3.5                                                        appearance      ⊚                                                                 ⊚                                           3 months                                                                      gloss retension 100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                    color difference                                                                              3.5                                                                              3.0                                                                              3.0                                                                              3.0                                                                              3.3                                                                              3.5                                                                              3.9                                                                              3.8                                                                              3.7                                                                              3.5                                                                              8.1                                                                              8.5                                                                              9.0                                                                              8.2                    appearance      ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚       __________________________________________________________________________

Powder Coating Composition

Examples 35-43

Components shown in Table 6 were mixed in a Henschcl mixer, followed bykneading under the conditions of an extrusion rate of 30 to 70 kg/H, atemperature of 80° to 120° C. and a rotational speed of 100 rpm by useof a BUSSCOKNEADER PR46 (Trade name, marketed by BUSS Co., Ltd.,Switzerland) kneader, removing the kneaded mixture in the form of a flatboard having a thickness of 3 to 6 mm, immediately cooling, roughlygrinding in a size of 2 to 3 mm, pulverizing by use of an atomizer(marketed by Fuji Sangyo Co., Ltd.), sieving by use of a 150 mechstandard sieve, and by removing coarse particles to obtain powdercoating compositions of Examples 35 to 43 respectively.

Comparative Examples 16-18

Comparative powder coating compositions of Comparative Examples 16-18were prepared in the same manner as in Example 35 by use of componentsshown in Table 6 respectively.

In Table 6, details of respective components are as follows. In Table 6,amounts of respective components in the formulation are represented byparts by weight respectively.

Resin:

Acrylic resin A: methyl methacrylate/styrene/n-butyl acrylate/glycidylmethacrylate=37/20/23/20 (weight ratio), weight average molecularweight: 7000, glass transition temperature: about 40°. Acrylic resin B:methyl methacrylate/styrene/n-butyl acrylate/hydroxyethylmethacrylate=41/15/24/20 (weight ratio), weight average molecularweight: 5,000, glass transition temperature: about 40°. polyester resinA: URALAC P-2400 (Trade name of carboxyl group-containing polyesterresin, marketed by DSM RESINS BV Co., Ltd.)

Curring Agent:

(*8) B-1530: Trade name of isophorone diisocyanate blocked withε-caprolactam, marketed by Daicell Hulls Co., Ltd.

                                      TABLE 6                                     __________________________________________________________________________                                             Comparative                                        Examples                   Examples                             Components and formulation                                                                  35 36 37 38 39 40 41 42 43 16 17 18                             __________________________________________________________________________    Resins                                                                        Acrylic resin A                                                                             100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100      100                                  Acrylic resin B                    100      100                               polyester resin A                     100      100                            Curing agent                                                                  dodecanoic diacid                                                                            20                                                                               20                                                                               20                                                                               20                                                                               20                                                                               20                                                                               20       20                                  B-1530(*3)                          20       20                               triglycidyl isocyanurate               7        7                             Silicon compounds                                                             tetraphenyl silicate                                                                            20                                                          tetraethyl silicate                                                                          10                40                                           tetraphenylethyl silicate                                                                          20                                                       methyl silicate 51(*)   20                                                    ethyl silicate 40(*)       20                                                 ethyl silicate 48(*)          20    20                                                                               20                                     __________________________________________________________________________

Film Appearance and Film Performance Tests

The powder coating composition of Example 35 was coated onto a zincphosphate-treated steel plate (08. mm in thickness) to be a cured filmthickness of about 60 μm by electrostatic powder coating process,followed by heating at 170° C. for 30 minutes to be evaluated as"non-treated". The above cured film was dipped into a 2.5 wt % aqueoussulfuric acid solution at 20° C. for 24 hours to be treated, followed bywashing the aqueous sulfuric acid solution adhered onto the film withwater, and by,drying at room temperature to be evaluated as "treated".

Separately, cured films were obtained in the same manner as in Example35 except that powder coating compositions of Examples 36-23 andcomparative powder coating compositions of Comparative Examples 16-18were used, and were evaluated as above.

Comparative Example 19

A cured film was formed in the same manet as in Comparative Example 16by use of the comparative powder coating composition of ComparativeExample 16, followed by coating tetraethyl silicate to be a thickness ofabout 10 μm onto the surface of the cured film, and drying at 20° C. for24 hours to be evaluated as above.

Results are shown in Table 7.

Test methods and evaluation criteria of appearance and performances forfilms obtained are shown by (*2) to (*6) to have the same meanings asabove respectively.

                                      TABLE 7                                     __________________________________________________________________________                      Examples                      Comparative Examples                            35    36 37 38 39 40 41 42 43 16 17 18 19                   __________________________________________________________________________    Treatment         non-                                                                             trea-                                                                            non-                                                                             non-                                                                             non-                                                                             non-                                                                             non-                                                                             non-                                                                             non-                                                                             non-                                                                             non-                                                                             non-                                                                             non-                                                                             non-                                   trea-                                                                            ted                                                                              trea-                                                                            trea-                                                                            trea-                                                                            trea-                                                                            trea-                                                                            trea-                                                                            trea-                                                                            trea-                                                                            trea-                                                                            trea-                                                                            trea-                                                                            treated                                ted   ted                                                                              ted                                                                              ted                                                                              ted                                                                              ted                                                                              ted                                                                              ted                                                                              ted                                                                              ted                                                                              ted                                                                              ted                     Adhesion properties(*2)                                                                         ◯                                                                    ◯                                                                    ◯                                                                    ◯                                                                    ◯                                                                    ◯                                                                    ◯                                                                    ◯                                                                    ◯                                                                    ◯                                                                    ◯                                                                    ◯                                                                    ◯                                                                    --                   Fabfricating properties(*3)                                                                     30 30 30 30 30 30 30 40 30 30 30 40 30 --                   Contact angle to water(*4)                                                                      64    62 63 62 62 58 61 58 59 92 90 89 **                   Film appearance prior to outdoor                                                                ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ◯        exposure(*5)                                                                  Outdoor exposure tests(*6)                                                    one month                                                                     gloss retension   100                                                                              100                                                                              -- -- -- -- -- -- -- -- -- -- -- --                   color difference  3.5                                                                              6.0                                                                              -- -- -- -- -- -- -- -- -- -- -- --                   appearance        ⊚                                                                 ⊚                                                                 -- -- -- -- -- -- -- -- -- -- -- --                   3 months                                                                      gloss retension   100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                  color difference  3.3                                                                              3.5                                                                              3.3                                                                              3.2                                                                              3.4                                                                              3.1                                                                              2.2                                                                              3.2                                                                              2.0                                                                              2.0                                                                              7.0                                                                              7.0                                                                              7.8                                                                              8.2                  appearance        ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ◯        6 months                                                                      gloss retension   98 98 97 97 98 97 98 99 97 98 98 97 67 --                   color difference  3.4                                                                              3.3                                                                              3.1                                                                              3.1                                                                              3.3                                                                              2.9                                                                              2.1                                                                              3.0                                                                              1.9                                                                              1.9                                                                              9.0                                                                              9.2                                                                              8.5                                                                              10 or more           appearance        ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 ⊚                                                                 X                    __________________________________________________________________________

We claim:
 1. A topcoating composition prepared by mixing a condensate ofan organosilicate represented by the general formula: ##STR5## wherein Ris the same or different and is a hydrogen atom or a monovalenthydrocarbon group having 1 to 10 carbon atoms, with an organic coatingcomposition containing, as a resin component, a reactively curableorganic resin consisting of a mixture of a hydroxyl group-containingbase resin with a polyisocyanate compound curing agent, said condensatehaving a degree of condensation of 2 to 10, said hydroxylgroup-containing base resin having a number average molecular weight of2,000 to 100,000 and a hydroxyl number of 20 to 200, the hydroxylgroup-containing base resin and the polyisocyanate compound being mixedin a ratio between the hydroxyl group-containing base resin and thepolyisocyanate compound such that an isocyanate group in thepolyisocyanate compound is in the range of 0.6 to 1.5 equivalents basedon hydroxyl group in the hydroxyl group-containing base resin, followedby being dried and cured to form a crosslinked organic film, a filmformed from said topcoating composition being such that a surface of thefilm, which has been subjected to an acid treatment, shows a contactangle to water of 70° or less.
 2. A topcoating composition as claimed inclaim 1, wherein the organic coating composition is an organic solventbased coating composition.
 3. A topcoating composition as claimed inclaim 1, wherein the organic coating composition is a powder coatingcomposition.
 4. A topcoating composition as claimed in claim 1, whereinR in the general formula of the organosilicate is a lower alkyl grouphaving 1 to 3 carbon atoms.
 5. A topcoating composition as claimed inclaim 1, wherein an amount of the organosilicate in formulation is inthe range of 0.1 to 50 parts by weight per 100 parts by weight of theresin solid content in the organic coating composition.
 6. A topcoatingcomposition as claimed in claim 1, wherein the contact angle is in therange of 20° to 65°.
 7. A treated film prepared by coating thetopcoating composition of claim 1 onto a substrate to form a film,followed by treating the surface of the film with an acid, a surface ofsaid treated film being hydrophilic and showing a contact angle to waterof 70° or less.